Post-retard fuel limiting strategy for an engine

Abstract

An engine ( 10 ) having a control system ( 24 ) that executes a control strategy ( 44 ) for limiting engine fueling upon deactivation of an engine retarder. Upon deactivation of the retarder, the strategy immediately shuts off fueling by setting the maximum fueling limit MFLMX to zero via setting of a latch function ( 42 ). Fueling continues to be shut off so long as the difference between a desired pressure for the hydraulic fluid used to force fuel into the engine combustion chambers and actual pressure of the hydraulic fluid (ICP — ERR) equals or exceeds a value (ICP — VRE — ERR) from a map ( 48 ) correlated both with the speed (N) at which the engine is running and with governed engine fueling (MFGOV) appropriate for the load on the engine at the engine running speed. Once that difference ceases to equal or exceed a value from the map ( 48 ), the latch function is reset, and the limit value for fueling provided by the strategy increases withtime according to a map ( 54 ).

1. A control system for an internal combustion engine comprising:
 a processor for processing various data to develop data for control of various engine functions, including control of hydraulic fluid pressure used by a fueling system to force fuel into engine combustion chambers and control of engine fueling; 
 wherein, upon the processor developing data calling for deactivation of an engine retarder that has been retarding the engine, the processor executes an algorithm that develops fueling limit data for imposing an initial limit on engine fueling and at a later time increasing the limit above the initial limit. 
 
   
   
     2. A control system as set forth in  claim 1  wherein upon the processor developing data calling for deactivation of the engine retarder, the processor executes the algorithm for imposing an initial limit of zero fueling on engine fueling and at a later time increasing the limit above the initial limit in accordance with a map of fueling limit values versus time. 
   
   
     3. A control system as set forth in  claim 1  wherein the algorithm repeatedly processes data representing engine running speed and governed engine fueling appropriate for the load on the engine at the engine running speed in accordance with a map of data values of hydraulic fluid pressure error correlated with sets of engine running speed and governed engine fueling data values, and processes a data value from the map and a data value representing difference between a desired pressure for the hydraulic fluid and actual pressure for the hydraulic fluid to develop a data value for a result that imposes the initial limit on engine fueling when the data value for the result indicates that difference between the desired hydraulic fluid pressure and actual hydraulic fluid pressure equals or exceeds the value from the map corresponding to the set of data for the speed at which the engine is running and governed engine fueling appropriate for the engine load at that engine running speed. 
   
   
     4. A control system as set forth in  claim 1  wherein the algorithm repeatedly processes data representing engine running speed and governed engine fueling appropriate for the load on the engine at the engine running speed in accordance with a map of data values of hydraulic fluid pressure error correlated with sets of engine running speed and governed engine fueling data values, and processes a data value from the map and a data value representing difference between a desired pressure for the hydraulic fluid and actual pressure for the hydraulic fluid to develop a data value for a result that increases the limit on engine fueling above the initial limit on engine fueling when the data value for the result indicates that difference between the desired hydraulic fluid pressure and actual hydraulic fluid pressure ceases to equal or exceed the value from the map corresponding to the set of data for the speed at which the engine is running and governed engine fueling appropriate for the engine load at that engine running speed. 
   
   
     5. A control system as set forth in  claim 4  wherein the algorithm increases the limit on engine fueling above the initial limit on engine fueling in accordance with a map of fueling limit values versus time. 
   
   
     6. A control system as set forth in  claim 5  wherein the algorithm sets the initial limit on engine fueling to zero fueling. 
   
   
     7. A control system as set forth in  claim 1  wherein the processor also processes data to develop other fueling limit data that is different from the fueling limit data for imposing an initial limit on engine fueling and at a later time increasing the limit above the initial limit, selects the smallest valued fueling limit data of all fueling limit data, and causes engine fueling to be limited in accordance with the smallest valued of all the fueling limit data.